In connection with motor vehicles, it is generally desirable to reduce force stresses and associated injuries to the occupants of the vehicle to the greatest possible extent in the event of a collision. For example, safety belts of the three-point type are generally used to secure the occupants of the vehicle. Such safety belts provide, in a known manner, a good protective effect and increased safety for the occupants in the event of a collision.
There are always drivers, however, who for various reasons choose not to use a safety belt. In order to also afford these drivers a certain degree of protection in the event of a collision, it has become desirable for the steering system of the vehicle to be adapted so that it is energy-absorbing. Furthermore, legislation in certain countries now requires the steering system in a vehicle to be designed to protect drivers who are thrown against the steering wheel of the vehicle in the event of a collision.
It is known that the steering system in a vehicle can be designed so that it absorbs energy when the driver of the vehicle is thrown forward and strikes the steering wheel during a collision. Such energy absorption can be brought about, for example, by the steering wheel being designed with deformable and flexible spokes. Furthermore, the main steering shaft of the vehicle can be arranged in a specially designed energy-absorbing steering column which is, in turn, mounted on the body of the vehicle. In the event of a collision, when the steering wheel, and consequently the steering column, are acted on by a very great force as a result of the driver being thrown forward, this force is transmitted from the steering wheel to the steering column. This results in the steering column being moved a certain distance in relation to the vehicle body. During this movement, energy is absorbed, which in turn reduces the stresses on the driver during the course of the crash.
In U.S. Pat. No. 4,978,138, apparatus for energy absorption in a steering system for vehicles is described. The apparatus functions according to the principle that if the driver is not secured by a seat belt, the steering system will absorb energy when the driver is thrown against the steering wheel in the event of a collision. For this purpose, the apparatus comprises a deformable, energy-absorbing plate which is connected to the steering column. In order to determine whether the driver has the seat belt on, a sensor is arranged in association with the fastening of the seat belt. This known apparatus also comprises a device for the protection of the knees of the driver, which device is activated depending on whether or not the driver is secured by the seat belt. If the driver is secured, the force from the knees of the driver will be absorbed by the knee protection device while the steering wheel is moved, by virtue of which the upper body and the head of the driver are prevented from striking the steering wheel.
The apparatus according to U.S. Pat. No. 4,978,138does have a disadvantage, however, in that it does not make allowance for the risk that even a driver who is secured with a safety belt can, under certain circumstances, actually strike the steering wheel during a collision. This can happen, for example, if the driver has the vehicle seat positioned in a far forward position or if the seat belt has an abnormally large amount of slack.
One object of the present invention is to produce an improved and simplified energy-absorbing apparatus for steering systems in motor vehicles. In particular, the present invention is intended to make available such a protective apparatus which comes into operation in the event of a collision irrespective of whether or not the driver of the motor vehicle is using a safety belt.